I am not a priest (obviously) so I do want to suggest to you that you can speak more about his with a priest as I trust he would have a better more solid answer to give rather than me…
I’m concerned about two possible separate things are going on…
One is that you are saying you are having something called intrusive thoughts. In which, you REALLY are sorry for the sins and something is nagging you, almost trying to bring you down into believing you are guilty, or whatever the intrusive thought is trying to tell you. These are to be ignored, but sometimes when they are they get stronger. If they get stronger, do not ignore them, agree with them sarcastically, then turn back to the Lord and kiss him with your love for Him in your heart stating how lowly you feel for being such a sinner. Intrusive thoughts wish to separate you from God and have no trust in Him. So when you lower your pride and agree BUT realize that God loves you just the same and wants you to confess and come to Him, then you “do them (intrusive thoughts) in” so to speak. They then have no material in which to try and drag you down.
The second concern I have is that you really are feeling that you were not sorry for your sins and that you are trying to cover up that fact within yourself. Covering up any feeling you have right or wrong will never help anyone. In fact, it will cause a lot of internal soul problems. It twists and rots and malforms the soul when we do that. We have to be honest with God. We can act this way out of fear for God and desire to be good which sometimes can be disguised pride. Its best to become absolutely humble before God and show the condition your heart, soul, mind is in- that is, if you have the inkling you are not all the way sorry for your sins, confess that. God desires that we become perfect, He does command that we do right, but I don’t think He expects it immediately. He wants us to respond to Him in truth and realness from within ourselves.
I want to say that if you are unsure about what might have or might not have been a sin, this is pretty clear cut in Catholic teaching. However, there is leniency for those who do not have full knowledge. We should always seek not to take advantage of that but seek to grow closer in understanding. “Seek God first”. Sometimes that understanding takes years, so just have yourself open to learning and doing God’s will. Ask the Holy Spirit to guide you.
Either way, (intrusive thoughts or hiding faults) it doesn’t invalidate the sacrament. Going to confession, even if you aren’t fully sorry but confess anyway, shows God that you are sorry that you did it enough to come and confess. If you were doing it to be crass and sarcastic, or mean, then yes I would say it would invalidate. But if you are going to God for help with your sins, and you feel remorse and want to change but don’t understand the depth of evil that your sin is in that you don’t entirely feel sorry, your confession is still valid. A willingness to do God’s will is necessary for it to be valid.
I hope I understood your question/concern correctly. I do want to reiterate to speak with a priest more about your concerns.